Weapon and Armor Proficiency: You are proficient with all simple weapons and with light armor but not with shields. Because the somatic components required for your spells aren’t as exact as other spells, you can cast spellthief spells while wearing light armor without incurring the normal arcane spell failure chance (though you still possess such a chance while wearing heavier armor)

Spellstrike (Su): You gain the Arcane Strike feat. You can also as a Standard action, make a Melee or Ranged touch attack (with a range of up to 30 feet) that deals damage as indicated on the table above. Alternately, you may add the indicated damage to any melee attack you make or ranged attack made from within 30 feet. In both cases, the damage is never multiplied with a critical hit. When making an attack using this class feature, you may sacrifice any number of dice of damage and select one of the following options :

Cast a Spell of a level maximum equal to the number of dice sacrificed. This spell is channeled by the attack and hit that target. If this is an area of effect, the spell is centered on the target.

Upon activating this ability, the spellthief automatically learns the names of all spells prepared or known by the target, if any. The spellthief may then choose to Steal a spell of a level maximum equal to the dice sacrificed. The target loses that spell from their memory if she prepares spells ahead of time, or one use of the appropriate spell slot if she is a spontaneous caster. If the stolen spell is cast spontaneously (such as spells cast by a sorcerer), the caster also loses the ability to cast the stolen spell for 1 hour. When a spell is stolen in this way, it is added to your list of spells known (see spells known, below) for 1 hour. if you are capable of casting spells of its spell level. Regardless of whether the stolen spell was a divine or arcane spell, it is cast as an arcane spell.

At any given time, you may possess a number of stored spells in this way equal to half of your class level + your Charisma modifier (minimum 1). If you would pass this limit, you instantly lose a stored spell of your choice. You may not steal more than one spell with a single attack.

Trapfinding (Ex): A Spellthief can use the Search skill to locate traps when the task has a Difficulty Class higher than 20. Finding a nonmagical trap has a DC of at least 20, or higher if it is well hidden. Finding a magic trap has a DC of 25 + the level of the spell used to create it. Spellthieves can use the Disable Device skill to disarm magic traps. A magic trap generally has a DC of 25 + the level of the spell used to create it. A spellthief who beats a trap’s DC by 10 or more with a Disable Device check can study a trap, figure out how it works, and bypass it (with his party) without disarming it.

Spells: You can cast a number of arcane spells, learned through your Spellstrike class feature, Absorb spell or a Spellbook. You can use a spell slot to cast any spell you have prepared of that level, just as a sorcerer can. To cast a spell, you must have a Charisma score equal to at least 10 + the spell level. The DC for a saving throw against one of your spells is 10 + spell level + your Cha modifier. Like other spellcasters, you can only cast a certain number of spells of each spell level per day. Your base daily spell allotment is given on the table above. In addition, you receive bonus spells per day if you have a high Charisma score.

Spells Known: You can prepare your spells knowns list from a Spellbook or add to that list using your Spellstrike or Absorb Spell features. You prepare that list as a Wizard prepare is spell but this list function as the spell knowns list of a sorcerer.

Spellgrace (Ex): A spellthief adds 1 point of their Charisma bonus (if any) per Spellthief class level to their Armor Class, CMD, Spell Resistance and any Saving Throw against spells, spell-like abilities, and magical traps.

Absorb Spell (Ex): You can absorb spells that fail to affect you. First of all, whenever you make a successful saving throw against a spell or spell-like ability that normally possesses a partial effect even with a successful save (such as “reflex half” or “fortitude partial”), you ignore the effect completely with a successful saving throw. Furthermore, whenever you make a successful saving throw against a spell, you may spend an immediate action to add the spell to your list of spells known as if through your Spellstrike class feature. If you succeeded on your saving throw by 5 points or more, you store the spell without using any action to do so.

Spellthief Talent : You can choose a talent from the Spellthief talent list each time ou gain this ability. Starting at level 10 you can choose talents from the Advanced Spellthieft talent list instead.

Discover Spells: Starting at 3rd level, your enhanced awareness of magic extends to your bursts of disruptive energy. Rather than selecting a specific spell when using Spellstrike, you gain awareness of all spells known or spells prepared possessed by the target with a spell level equal to or less than the number of sacrificed dice and you may choose freely from among them.

Steal Spell-Like Abilities (Su): You can use your Spellstrike to steal more innate forms of magic, stealing spell-like abilities. When hitting an opponent and dealing Spellstrike damage, you may choose to forego any number of dice of damage and elect to steal a spell-like ability. Much like when stealing spells, you learn all spell-like abilities that the target possesses remaining uses for and may select any of them with a spell level up to the number of sacrificed dice. If the target can’t use a spell-like ability at the present time (such as a summoned demon’s summon ability), you can’t steal it.
The target loses a single use of the ability you select and loses the ability to use it further for one hour, until it is replaced, or until you expend its energy. When a spell-like ability is stolen in this way, it is added to your list of spells known if it appears on any spell list and is of a spell level you are capable of casting (if it is unclear what spell level the spell-like ability is, use the highest of all spell levels of spell lists it appears on). Either way, you gain a single use of the spell-like ability to use within the next hour if you possess a Charisma score of at least 10 + the spell level. You use your own class level in place of the target’s caster level and use your Charisma score to determine the spell’s DC. Though it is used as a spell-like ability, you must still provide any expensive material components or foci as well as any XP cost. A spell-like ability stolen in this way counts as a stored spell. You may not steal more than a single spell-like ability with a single attack.

Bypass Wards (Su): Your disruptive powers allow you to overcome most forms of magical defense in existence. You are incapable of setting off magical traps and add half of your class level to your AC and saving throws against magical traps (this stacks with your spellgrace class feature). Furthermore, when attacking or making other aggressive actions, you ignore all miss chances and bonuses to AC and/or saving throws that targets have gained through magical (but not supernatural) means.

Improved Bypass Wards (Su): Starting at 14th level, magical traps (such as fireball traps and explosive runes), spell effects that target objects (such as arcane lock and hardening), and spell effects that target areas (such as Improved guards and wards and forbiddance) fail to function within 10 feet of you as if suppressed by an antimagic field. Furthermore, when attacking or making other aggressive actions, you ignore all damage reduction, regeneration, spell resistance, energy resistances, and immunities that the target has gained through magical (but not supernatural) means.

Steal Energy Resistance (Su): Starting at 8th level, your disruptive energies can steal some of the defenses of a creature they come into contact with. When hitting an opponent and dealing mystic siphon damage, you may choose to forego any number of dice of damage and instead gain a separate benefit. You learn all forms of energy resistance and immunity that the target possesses and select any number of such immunities or resistances. The target’s resistance to each selected form of energy is reduced by 5 for every dice of damage sacrificed in this way, to a minimum of 0 (immunities are not reduced).
For each resistance and immunity targeted in this way, you gain energy resistance equal to the amount of resistance lost by your target (in the case of immunities, you gain energy resistance 5 per dice of damage sacrificed). Each resistance gained in this way is stored as a stolen spell (counting towards your normal maximum) for 1 hour, until it is replaced, or until the effect granting the target their energy resistance/immunity ends (whichever comes first). At this time, the original target regains their energy resistance they have lost (unless you have lost the energy resistance because an effect ended).
Multiple sources of energy resistance against the same form of energy do not stack.

Steal Spell-Like Abilities (Su): You can use your Spellstrike to steal more innate forms of magic, stealing spell-like abilities. When hitting an opponent and dealing Spellstrike damage, you may choose to forego any number of dice of damage and elect to steal a spell-like ability. Much like when stealing spells, you learn all spell-like abilities that the target possesses remaining uses for and may select any of them with a spell level up to the number of sacrificed dice. If the target can’t use a spell-like ability at the present time you can’t steal it. The target loses a single use of the ability you select and loses the ability to use it further for one hour. When a spell-like ability is stolen in this way, it is added to your list of spells known if it appears on any spell list and is of a spell level you are capable of casting (if it is unclear what spell level the spell-like ability is, use the highest of all spell levels of spell lists it appears on).

Steal Energy Resistance (Su): Your disruptive energies can steal some of the defenses of a creature they come into contact with. When hitting an opponent and dealing Spellstrike damage, you may choose to forego any number of dice of damage and instead gain a separate benefit. You learn all forms of energy resistance and immunity that the target possesses and select any number of such immunities or resistances. The target’s resistance to each selected form of energy is reduced by 5 for every dice of damage sacrificed in this way, to a minimum of 0 (immunities are not reduced). For each resistance and immunity targeted in this way, you gain energy resistance equal to the amount of resistance lost by your target (in the case of immunities, you gain energy resistance 5 per dice of damage sacrificed). Each resistance gained in this way is stored as a stolen spell for 1 hour or until the effect granting the target their energy resistance/immunity ends (whichever comes first). At this time, the original target regains their energy resistance they have lost (unless you have lost the energy resistance because an effect ended).Multiple sources of energy resistance against the same form of energy do not stack.

Steal Spell Resistance (Su): A spellthief can use a Spellstrike to temporarily steal some or all of a creature's spell resistance. A spellthief who hits an opponent with a spellstrike can choose to forgo 3d6 points of spellstrike damage and instead reduce the target's spell resistance by an amount equal to the spellthief's level. The spellthief also gains spell resistance equal to 10 + the amount stolen, up to a maximum of the value equal to the original spell resistance of the target. If the target is willing, a spellthief can steal spell resistance with a touch as a standard action.
The stolen spell resistance benefits the spellthief for a number of rounds equal to his Intelligence modifier, and then returns to the target creature. If the spell resistance is derived from a temporary effect, the stolen spell resistance disappearsw hen the effect would normally end. A spellthief can't use this ability on the same creature until the stolen spell resistance returns.

Steal Healing: Any form of healing or temporary hit points that the target receives for the next 5 minutes is instead applied to the spellthief. This includes fast healing, regeneration, healing from spells or other similar effects, healing from magic weapons, etc.

Steal Supernatural Ability: Upon activating this ability, the spellthief automatically learns the names of all supernatural abilities that the target creature has. The spellthief may then choose any one of these supernatural abilities to steal. The spellthief may not steal a supernatural ability from a creature with hit dice greater then his spellthief class level. The target loses this supernatural ability for 5 minutes, and the spellthief gains the ability for 5 minutes. If the supernatural ability duplicates a spell with that has an expensive material component (over 1 gp or any amount of xp), then the spellthief must provide such components in order to use the supernatural ability.

Nondetection (Su): Starting at 9th level, the spellthief has learned to hide themselves from divination spells, as if under the effect of a continuous Nondetection spell. He is also always aware of any attempt to magically observe him, as if under a continuous Detect Scrying spell. For the purpose of determine these effects, the caster level is equal to the spellthief's class level. The spellthief may only use this ability on themselves (which also effects gear that stays in their possession), and not on any other creature or object.
In addition, all spell cast by the spellthief no longer require verbal components, as if using the Silent Spell feat. Spells cast using this ability do not increase in spell level or casting time.

Dimensional Anchor (Su): Starting at 15th level, enemies within 60 feet of the spellthief cannot use any magical means of movement, travel, or teleportation. This includes magical flight, extradimensional travel, astral projection, blink, dimension door, ethereal jaunt, etherealness, gate, maze, plane shift, shadow walk, teleport, and any similar spells, spell-like abilities, or supernatural abilities within DM approval. If an enemy is using any such ability when they come with 60 feet of the spellthief, they are suppressed as if they had entered an Antimagic Field, with a caster level equal to the spellthief's class level. (Although all other magical effects continue normally).
This ability does not interfere with creatures who are inherently astral, ethereal, or incorporeal (such as a ghost), nor does it block extradimensional perception or attack forms. It also does not prevent summoned creatures from disappearing at the end of a summoning spell. The spellthief may suppress or reinitiate this ability as an Immediate Action.

Steal Spell Effect (Su): Beginning at 12th level, your disruption of magical powers can siphon an active spell effect from another creature. When hitting an opponent and dealing Mystic siphon damage, you may choose to forego any number of dice of damage and instead gain a separate benefit. You instantly learn all spell effects active on the target with a spell level equal to or less than the number of sacrificed dice and may select any number of them to transfer to yourself. You can’t steal a spell effect if its caster level exceeds your class level + your Charisma modifier.
Upon stealing one or more spell effects, you gain the stolen effect (and the original creature loses that effect) and each spell effect is stored as a stolen spell (though you can’t cast the spell once more, it still counts towards your maximum number of stolen spells) for 1 hour, until it is replaced as a stolen spell, or until the effects normal duration has ended (whichever comes first). If the spell effect’s duration hasn’t expired by the time it’s been replaced or an hour has passed, the spell effect returns to its original target.
You can steal the effect of a spell only if it could be originally cast upon you by the original caster (meaning, among other things, that you can’t steal spell effects with a range of personal). If you try to steal the effect of a spell that can’t affect you, the effect is still suppressed for 1 hour, until you replace it, or until its duration ends.
This ability does not work on spell effects that are immune to dispel magic (such as bestow curse)

Steal Summons: If the target hit and damaged by the Backstab exists on this plane as a result of magic (such as Summon Monster, Summon Nature's ally, Animate Undead, Animate Objects, a Summoner's Eidolon, a Paladin's Special Mount, or any similar magical ability, spell, spell-like ability, or supernatural ability) and is currently being controlled by another creature, then that control is lost for up to 5 minutes. The spellthief gains control of the target for 5 minutes as if he were the original summoner/caster. The spellthief may also choose to dismiss the target creature if it would normally be possible for the original summoner/caster to do so.

Steal Defenses (Su): Starting at 16th level, you can use your mystic siphoning to steal the physical and magical defenses of targets. When hitting an opponent and dealing mystic siphon damage, you may choose to forego any number of dice of damage and elect to steal either spell resistance or damage reduction. If stealing damage reduction, the target’s damage reduction is reduced by 2 for each dice of damage sacrificed. If stealing spell resistance, the resistance is reduced by 5 for each dice of damage sacrificed. Neither value may be reduced below 0 and thefts of either kind last for 1 hour, until they are replaced, or until a temporary effect granting the damage reduction or spell resistance ends.
If you stole damage reduction, you gain unsurpassable damage reduction (damage reduction X/-) with a value equal to the amount of stolen damage reduction. If you instead stole spell resistance, you gain spell resistance equal to the amount of spell resistance you have stolen. In either case, these benefits only last for the normal duration of this ability. Both kinds of theft count as stored spells. You may not acquire both damage reduction and spell resistance with a single attack

Reflect Spell (Su): Starting at 18th level, if the spellthief successfully absorbs a spell with his Absorb Spell ability, then he may cast that spell as an Immediate Action. He must do so immediately after absorbing the spell, otherwise it is stored and can only be cast using it's normal casting time.

X-Ray Vision (Su): Starting at 19th level, the spellthief gains the ability to see into and through non-living solid matter. The range of this X-Ray Vision is 30 feet, seeing as if he were looking at something in normal light even if there is no illumination. His ability to Sense Magic (and thus Detect Magic, know which enemies he can Steal from, and detect magical traps) and any relevant active Mystic Senses (such as See Invisibility, True Seeing, etc) also function through up to 30 feet of solid matter. He may also look through layers of solid matter with a high level of discernment. For example he could see the treasure inside of a chest or items inside of a backpack. The spellthief may use or suppress this ability at will as a free action.Steal Essence (Su): Starting at 20th level, if the spellthief kills a creature with a Backstab and successfully uses any Steal Ability on that creature, he may choose to steal the ability for up to 24 hours. If the stolen ability comes from a temporary effect (such as a spell or a magic item with a limited duration), then the spellthief still automatically loses it when the remaining duration expires. The spellthief may only have one stolen essence at any given time. He cannot use this ability again until the duration of the previous stolen ability has expired (24 hours, or less if it was a temporary effect).